Preparation method and application of double-active-site integrated catalyst

Abstract

The invention relates to a preparation method and application of a double-active-site integrated catalyst. According to the method, a self-template method and an in-situ reduction method are utilized, MNPs and polyion liquid are organically combined to prepare confinement anchored MNPs radial channel hollow SiO2 microspheres, imidazole polyion liquid is introduced through surface modification and graft polymerization, construction of the radial channel double-shell PILs-MNPs integrated double-site catalyst is achieved, the site of MNPs catalyzes olefin epoxidation, the site of MNPs is introduced into the radial channel double-shell PILs-MNPs is introduced into the radial channel double-shell PILs-MNPs, and the site of the radial channel double-shell PILs-MNPs is introduced into the radial channel double-shell PILs-MNPs integrated double-site catalyst. The imidazole ionic liquid site is used for catalyzing cycloaddition of epoxide and CO2. The two-site catalyst prepared by the invention has a catalytic yield of 92% in serial catalytic conversion of CO2 under the conditions of 90 DEG C and 1MPa CO2, the catalytic yield after 10 cycles can still reach 89%, and the two-site catalyst has good recovery activity and cycle stability.

Description

Technical Field

[0001] The technical solution of this invention relates to the field of preparation of tandem catalysts for olefin epoxidation and carbon dioxide cycloaddition, specifically to a method for preparing a dual-active-site integrated catalyst PILs-MNPs with radially porous bishell polyionic liquids (PILs) and noble metal nanoparticles (MNPs) and its application. Background Technology

[0002] Against the backdrop of the global push for sustainable development and green chemistry, how to achieve efficient resource utilization and environmentally friendly chemical transformation has become a core research topic (Nat. Sustain. 2023, 6(5), 502-512). With the continuous acceleration of industrialization, various human activities have led to massive emissions of greenhouse gases, placing a heavy burden on the ecological environment. Global warming and frequent extreme weather events are becoming increasingly serious problems (Nat. Rev. EarthEnviron. 2025, 6(2), 86-105). Carbon dioxide (CO2), as a major component of greenhouse gases, has seen its emissions continuously rise, attracting significant attention. However, CO2 is also an abundant, stable, and non-toxic C1 resource. How to transform it into high-value-added products has become a key problem urgently needing to be solved in the field of chemistry.

[0003] Among numerous CO2 conversion strategies, the preparation of cyclic carbonates via the cycloaddition reaction of epoxides with CO2 is a promising method (Chem. Soc. Rev. 2024, 53(19), 9609-9651). This reaction produces almost no byproducts and achieves 100% atom utilization, making it a typical green chemistry reaction (Adv. Mater. 2024, 36(38), 2406610). Furthermore, cyclic carbonates have wide applications in industrial production, such as battery electrolytes, clean polar solvents, cosmetic additives, and metal extractants (Energy Environ. Sci. 2024, 17(22), 8756-8775). However, the epoxides used as reactants are highly toxic, flammable, explosive, and costly, and require sophisticated reaction equipment, severely limiting the industrial scale of cyclic carbonates. Therefore, if cyclic carbonates can be synthesized from inexpensive and less toxic olefins via a tandem reaction of olefin epoxidation and in-situ CO2 cycloaddition, the separate synthesis and separation steps of epoxides can be avoided, effectively reducing production costs. Currently, the bottleneck in traditional cyclic carbonate synthesis processes lies mainly in the difficulty of constructing an efficient tandem catalytic system (Science 2021, 371(6535), 1203-1204).

[0004] Currently, various polyionic liquids have been reported as heterogeneous catalysts for the synthesis of cyclic carbonates from CO2. Patent CN119735790A, entitled "A Dihydroxy Functionalized Hypercrosslinked Polyionic Liquid and Its Preparation Method and Application," proposes a dihydroxy functionalized hypercrosslinked polyionic liquid. This liquid introduces different benzene ring structures (benzene and biphenyl) into the catalyst based on the introduction of dihydroxy functional groups, forming different porous structures to catalyze the synthesis of cyclic carbonates from carbon dioxide and epoxides. However, it suffers from drawbacks such as limited functionality, reliance on epoxides as raw materials, and a lack of precise control over the pore structure and spatial distribution of active sites.

[0005] Single catalytic sites typically catalyze only one specific type of reaction. Therefore, to address existing problems and achieve olefin epoxidation and CO2 in-situ cycloaddition reactions, it is necessary to construct dual-site catalysts (Nat. Rev. Methods Primers 2023, 3(1), 28). Multi-site catalysts (MNPs) possess abundant active surface atoms and high specific surface area, combining the advantages of recyclability in heterogeneous catalysis and high conversion frequency in homogeneous catalysis, making them ideal sites for olefin epoxidation. Polymerized ionic liquids (PILs) are polymerized from ionic liquid monomers, retaining the ionic characteristics of ionic liquids and exhibiting catalytic performance close to that of homogeneous catalysts (Appl. Catal. B 2022, 313, 121463), while also possessing the recyclability of heterogeneous catalysis, making them the optimal choice for CO2 cycloaddition reactions. The organic combination of MNPs and PILs is an effective means to achieve the tandem synthesis of cyclic carbonates through olefin epoxidation and CO2 in-situ cycloaddition reactions. By employing rational structural engineering design, MNPs and PILs are precisely arranged within micro- and nano-scale spaces. This approach stabilizes MNPs, enhances mass transfer, and fully leverages the high catalytic activity of MNPs and PILs, which are similar to homogeneous catalysts. Utilizing synergistic catalytic capabilities to achieve the tandem transformation of olefin epoxidation and CO2 cycloaddition is a research topic of significant importance and considerable challenge. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of current technologies by providing a method for preparing integrated catalysts with dual active sites. This method utilizes a self-templating method and an in-situ reduction method to organically combine micronutrient polymers (MNPs) with polyionic liquids (PILs) to prepare confined, anchored MNPs-containing radially porous hollow SiO2 microspheres. Imidazole-based PILs are then introduced through surface modification and graft polymerization, achieving the construction of a previously unreported radially porous, double-shelled PILs-MNPs integrated dual-site catalyst. In this catalyst, the MNP sites catalyze the epoxidation of olefins, while the imidazole-based PIL sites catalyze the cycloaddition of epoxides with CO2. The catalyst obtained by this invention exhibits synergistic micro / nanostructure effects of the dual active sites of MNPs and imidazole-based PILs, fully demonstrating high catalytic activity. It has significant application value in the green synthesis of cyclic carbonates and provides a new strategy and scientific basis for the efficient catalytic conversion of CO2 under mild conditions.

[0007] The technical solution of this invention is:

[0008] A method for preparing a dual-active-site integrated catalyst, the method comprising the following steps:

[0009] 1) Preparation of SiO2 hollow porous microspheres with an average particle size range of 50–500 nm

[0010] Isopropanol, hexadecyltrimethylammonium bromide (CTAB), and water were added to a reactor and sonicated until homogeneous. The system was heated to 70–90 °C under stirring, and vinyltrimethoxysilane (VTMS) was added. The mixture was stirred for 20–40 min, followed by the sequential addition of ammonia, tetraethyl orthosilicate (TEOS), and cyclohexane. The reaction was carried out under stirring for 10–15 h, after which the reaction was stopped. The material was centrifuged and settled, washed alternately with ethanol and water, and dried to obtain SiO2 hollow porous microspheres (HPMSs).

[0011] The volume ratio of water:isopropanol:VTMS:ammonia:TEOS:cyclohexane is 130:10-50:0.5-5:1-10:1-5:10-25.

[0012] Add 0.5–1.0 g of CTAB to every 130 mL of water;

[0013] The concentration of ammonia water is 25-30 wt%.

[0014] The stirring speed is 100-200 rpm, and the centrifugation speed is 500-2000 rpm.

[0015] 2) Preparation of HPMSs / MNPs composite structure by in-situ reduction method

[0016] The SiO2 hollow porous microspheres obtained in the previous step were dispersed in water at room temperature and added to a mixed solution containing chloroauric acid (HAuCl4·4H2O), H2O, and polyvinylpyrrolidone (PVP). The mixture was ultrasonically dispersed until homogeneous, and then NaBH4 solution was added dropwise until the solution turned purple. The reaction product was centrifuged and dried to obtain radially porous hollow microspheres loaded with metal nanoparticles.

[0017] The mass ratio of HAuCl4·4H2O solution:H2O:PVP = 0.01~0.03:100~200:0.2; each 1g of SiO2 hollow porous microspheres is dispersed in 100~200mL of water;

[0018] The concentration of the HAuCl4·4H2O solution is 0.01–0.1 wt%.

[0019] The concentration of the NaBH4 solution was 0.001–0.02 wt%.

[0020] 3) Graft polymerization to prepare HPMSs / MNPs@PILs dual-site tandem catalyst

[0021] Hollow SiO2 microspheres obtained in the previous step, water, 1,4-divinylbenzene (DVB), PVP, 1-vinyl-3-ethylimidazolium bromide (VEI-Br), and potassium persulfate (KPS) were added sequentially to the reactor. The system was heated to 60-80°C under stirring and the reaction was stopped after 10-12 hours. The material was centrifuged and settled, washed alternately with ethanol and water, and dried to obtain the HPMSs / MNPs@PILs dual-site tandem catalyst.

[0022] The mass ratio of hollow SiO2 microspheres: DVB: PVP: VEI-Br: KPS = 10~20: 100~150: 10: 100~150: 1~5;

[0023] 0.05–0.1 g of potassium persulfate is dissolved in every 100 mL of water.

[0024] The dual-active-site integrated catalyst prepared by the method is used as a catalyst in a tandem reaction of olefin epoxidation and CO2 in-situ cycloaddition.

[0025] Specifically, the steps include the following:

[0026] The prepared dual-active-site integrated catalyst, reaction substrate, tert-butyl hydroperoxide (TBHP) and N,N-dimethylformamide (DMF) were added to a high-pressure reactor and mixed. After sealing, CO2 was introduced into the reactor and pressurized. The mixture was stirred at 80-100°C for 10-20 hours to obtain the product styrene cyclic carbonate.

[0027] The reaction substrates are styrene, p-methylstyrene, divinylbenzene, or m-methylstyrene.

[0028] Each 2 mL of DMF contains 50–100 mg of a dual-active-site integrated catalyst, 1–3 mmol of styrene, and 1–10 mmol of TBHP; the CO2 pressure is 0.8–1.5 MPa.

[0029] The essential features of this invention are:

[0030] Traditional catalysts have limitations in active site exposure and mass transfer efficiency, making it difficult to achieve efficient tandem catalysis. This invention combines self-templating, sol-gel, and in-situ reduction methods to prepare hollow microspheres with a centrally radial pore structure. These microspheres, through their confinement effect, segment and anchor nanoparticles, which are then coated with a polyionic liquid to construct a hollow, porous core-shell structured ionic liquid-nanoparticle integrated dual-site tandem catalyst. By integrating two sites, the diffusion path is shortened. Utilizing the synergistic effect of the nanostructure and active sites, the limitations of traditional single-site or simple combinations are overcome, achieving efficient mass transfer and full exposure of active sites, significantly improving catalytic efficiency.

[0031] The beneficial effects of this invention are:

[0032] (1) This invention proposes a catalyst for tandem catalytic carbon dioxide conversion, namely a method for preparing a radially porous bishell PILs-MNPs integrated dual-site catalyst. Nanoparticles possess abundant active surface atoms and high specific surface area, combining the advantages of recyclability in heterogeneous catalysis and high conversion frequency in homogeneous catalysis, making them ideal sites for olefin epoxidation. Polyionic liquids are polymerized from ionic liquid monomers, retaining the ionic characteristics of ionic liquids, exhibiting catalytic performance close to that of homogeneous catalysts, while also possessing the recyclability of heterogeneous catalysis, making them the optimal choice for CO2 cycloaddition reactions. The bottleneck of traditional cyclic carbonate synthesis processes lies mainly in the difficulty of constructing efficient tandem catalytic systems. Therefore, precisely arranging MNPs and PILs in micro-nano spaces can stabilize MNPs and enhance mass transfer, fully leveraging the high catalytic activity of MNPs and PILs similar to homogeneous catalysts, and utilizing synergistic catalytic capabilities to achieve tandem conversion of olefin epoxidation and CO2 cycloaddition. This method is easy to scale up and industrialize, showing good industrial development prospects.

[0033] (2) This invention constructs a radially porous double-shell structure. On one hand, it constructs hollow porous microspheres with radially pored channels, connecting the radially pored channels with the hollow cavity. This shortens the substrate diffusion path and improves the substrate enrichment capacity of the hollow cavity, further enhancing the mass transfer effect. On the other hand, it utilizes the confinement effect of the radially pored channels to segment and anchor MNPs, inhibiting NP aggregation and sintering, and exposing active sites. Through graft polymerization to coat porous PILs, a radially porous double-shell hollow structure is constructed, further protecting MNPs from detachment and improving cycling stability. Based on the confinement effect of the radially pored channels on the microspheres, the precursor chloroauric acid can be reduced to AuNPs in situ within the channels without surface modification, segmenting and anchoring them in different channels. Ultimately, a hollow porous microsphere / gold nanoparticle (HPMSs / Au NPs) composite structure was successfully prepared. (See attached...) Figure 5 and 6 It can be seen that the prepared HPMSs / AuNPs exhibit good dispersibility and stability of gold nanoparticles.

[0034] (3) Inspired by acid-base synergistic catalysis, this invention utilizes radially porous hollow microspheres coated with polyionic liquid as the framework and metal nanoparticles as the synergistic active component to achieve the rational design and controllable preparation of a polyionic liquid dual-site catalyst supported on metal nanoparticles. The polyionic liquid provides nucleophilic sites for catalyzing CO2 cycloaddition, while the metal nanoparticles provide Lewis acid sites for catalyzing olefin epoxidation. Under conditions of 90℃ and 1MPa CO2, the catalytic yield of this catalyst, as measured by gas chromatography, was 92%, and the yield remained at 89% after 10 cycles, indicating that this dual-site integrated catalyst possesses excellent recovery activity and cycling stability. The dual-site catalyst prepared in this invention exhibits excellent performance and broad application prospects in the field of tandem catalytic conversion of CO2. Attached Figure Description

[0035] Figure 1 Schematic diagram of the preparation process of HPMSs / MNPs@PILs;

[0036] Figure 2 SEM images of SiO2 hollow radial porous microspheres (HPMSs) in Example 1;

[0037] Figure 3 TEM image of SiO2 hollow radial porous microspheres (HPMSs) in Example 1;

[0038] Figure 4 XRD diffraction pattern of hollow porous microspheres / gold nanoparticles in Example 1;

[0039] Figure 5 SEM images of hollow porous microspheres / gold nanoparticles in Example 1;

[0040] Figure 6 HAADF-STEM image of hollow porous microspheres / gold nanoparticles in Example 1;

[0041] Figure 7 SEM images of hollow porous microspheres / gold nanoparticles@polyionic liquid in Example 1;

[0042] Figure 8 Example 1: SEM images of hollow porous microspheres / gold nanoparticles@polyionic liquid under high pressure;

[0043] Figure 9 Gas chromatogram of the catalytic product in Example 1;

[0044] Figure 10 Bar graph showing the change in catalyst yield with the number of cycles under the same conditions (90°C, 1 MPa, 10 h) in Example 1. Detailed Implementation

[0045] The preparation process of this invention is as follows: Figure 1 As shown, (1) HPMSs were prepared by a self-templating method and a sol-gel method using tetraethyl orthosilicate and vinyltrimethoxysilane as silicon sources, and isopropanol, cyclohexane and hexadecyltrimethylammonium bromide as structure directing agents. (2) HPMSs / MNPs composite structures were prepared by confining and anchoring MNPs within HPMSs using an in-situ reduction method. (3) HPMSs / MNPs@PILs dual-site tandem catalysts were prepared by surface modification and graft polymerization. The dual-active-site integrated catalysts prepared by the above method are used as catalysts in tandem reactions of olefin epoxidation and CO2 in-situ cycloaddition.

[0046] The preparation process of this invention is simple and easy to prepare on a large scale. The resulting product has excellent photothermal conversion performance and highly active multifunctional sites. The radial pore double-shell hollow structure makes it easy to expose more internal active sites and improve mass transfer efficiency. The dual sites of polyionic liquid and metal nanoparticles are conducive to increasing synergistic catalytic ability. These characteristics make it have great potential application value in the fields of tandem catalysis and synergistic catalysis.

[0047] Among them, the tetraethyl orthosilicate, vinyltrimethoxysilane, cyclohexane, hexadecyltrimethylammonium bromide, 1,4-divinylbenzene, polyvinylpyrrolidone and functionalized ionic liquid monomer 1-vinyl-3-ethylimidazolium bromide are known materials.

[0048] Example 1:

[0049] (1) Preparation of SiO2 hollow porous microspheres with an average particle size range of 300 nm

[0050] In a three-necked flask, 130 mL of water, 40 mL of isopropanol, and 0.8 g of cetyltrimethylammonium bromide (CTAB) were added sequentially. The mixture was sonicated until completely homogeneous. The system was heated to 80 °C with a stirring speed of 100 rpm. 0.85 mL of vinyltrimethoxysilane (VTMS) was added, and the mixture was stirred at 200 rpm for 30 min. Then, 10 mL of 28 wt% ammonia, 2.5 mL of tetraethyl orthosilicate, and 20 mL of cyclohexane were added sequentially. The mixture was stirred at 180 rpm and reacted at 80 °C for 12 h. The material was centrifuged at 1000 rpm to settle, washed alternately with ethanol and water, and dried to obtain SiO2 hollow porous microspheres (HPMSs).

[0051] Appendix Figure 2 The image shows a SEM image of hollow porous SiO2 microspheres obtained by scanning with a FEI Nano SEM 450 scanning electron microscope. The image shows that the SiO2 microspheres have a porous structure with a size of about 300 nm.

[0052] Appendix Figure 3 The images are TEM images obtained by characterizing SiO2 hollow porous microspheres using a FEI Talos F200S transmission electron microscope. As can be seen from the images, the SiO2 microspheres exhibit a radial channel structure.

[0053] (2) Preparation of HPMSs / MNPs composite structure by in-situ reduction method

[0054] At room temperature, 1 g of SiO2 hollow porous microspheres obtained in the previous step were added to a mixed solution containing 15 mg of 0.03 wt% chloroauric acid (HAuCl4·4H2O) solution, 150 g of water, and 0.2 g of polyvinylpyrrolidone (PVP). The mixture was ultrasonically dispersed until homogeneous. Subsequently, 0.01 wt% NaBH4 solution was added dropwise until the solution turned purple. The reaction product was centrifuged and dried to obtain radially porous hollow microspheres loaded with metal nanoparticles.

[0055] Appendix Figure 5 The image shows a SEM image of the hollow porous microsphere / gold nanoparticle composite structure obtained by scanning with a FEI Nano SEM 450 scanning electron microscope. The image shows that the SiO2 hollow porous microspheres are distributed with high-brightness metallic particles, indicating the presence of Au NPs (white particles).

[0056] Appendix Figure 6 The image shows a spherical aberration-corrected HAADF-STEM image obtained by characterizing the hollow porous microsphere / gold nanoparticle composite structure using a Titan Themis Cubed G260-300 spherical aberration-corrected transmission electron microscope. The image shows that the gold nanoparticles are uniformly distributed within the radial channels of the SiO2 microspheres.

[0057] (3) Graft polymerization to prepare HPMSs / MNPs@PILs dual-site tandem catalyst

[0058] In a three-necked flask, 0.1 g of hollow SiO2 microspheres loaded with gold nanoparticles, 40 mL of water, 1 g of 1,4-divinylbenzene (DVB), 0.1 g of PVP, 1 g of 1-vinyl-3-ethylimidazolium bromide (VEI-Br), and 0.03 g of potassium persulfate were added sequentially. The system was heated to 70 °C under stirring and the reaction was stopped after 10 h. The material was centrifuged and settled, washed alternately with ethanol and water, and dried to obtain the HPMSs / MNPs@PILs dual-site tandem catalyst.

[0059] Appendix Figure 7 The image shows a SEM image of the hollow porous microsphere / gold nanoparticle@polyionic liquid composite structure obtained by scanning with a FEI Nano SEM 450 scanning electron microscope. The image shows that the surface of the hollow porous microsphere / gold nanoparticle is coated with a layer of polyionic liquid.

[0060] Appendix Figure 8 The image shows a hollow porous microsphere / gold nanoparticle@polyionic liquid composite structure obtained by scanning the hollow porous microsphere / gold nanoparticle@polyionic liquid composite structure under high pressure using a FEI Nano SEM 450 scanning electron microscope. The image shows that a radially porous double-shell hollow structure was constructed.

[0061] The dual-active-site integrated catalyst prepared by the method is used as a catalyst in a tandem reaction of olefin epoxidation and in-situ CO2 cycloaddition, and specifically includes the following steps:

[0062] 50 mg of the prepared dual-active-site integrated catalyst, 1 mmol of styrene, 1 mmol of tert-butyl hydroperoxide (TBHP) and 2 mL of N,N-dimethylformamide (DMF) were added to a high-pressure reactor and mixed. After sealing, CO2 was introduced into the reactor and the pressure was increased to 1 MPa. The mixture was stirred at 90 °C for 10 h to obtain the product styrene cyclic carbonate.

[0063] Figure 9 The image shows the gas chromatogram of the catalytic product obtained using an Agilent GC 8860 gas chromatograph. The figure shows that the catalytic yield of the catalyst is 92% under the conditions of 90℃ and 1MPa CO2.

[0064] Figure 10 The bar chart shows the catalytic yield as a function of the number of cycles under the same catalytic conditions (90℃, 1MPa, and 10h). The chart shows that the catalytic yield can still reach 89% after 10 cycles, indicating that the dual-active-site integrated catalyst has good recovery activity and cycle stability.

[0065] Example 2:

[0066] (1) Preparation of SiO2 hollow porous microspheres with an average particle size range of 200 nm

[0067] In a three-necked flask, 130 mL of water, 30 mL of isopropanol, and 0.8 g of cetyltrimethylammonium bromide (CTAB) were added sequentially. The mixture was sonicated until completely homogeneous. The system was heated to 80 °C with a stirring speed of 100 rpm. 0.85 mL of vinyltrimethoxysilane (VTMS) was added, and the mixture was stirred vigorously at 200 rpm for 30 min. Then, 10 mL of 28 wt% ammonia, 2.5 mL of tetraethyl orthosilicate, and 20 mL of cyclohexane were added sequentially. The mixture was stirred at 180 rpm and reacted at 80 °C for 12 h. The material was centrifuged at 100 rpm to settle, washed alternately with ethanol and water, and dried to obtain SiO2 hollow porous microspheres (HPMSs).

[0068] (2) The in-situ reduction method was used to prepare the HPMSs / MNPs composite structure, following the same steps as in Example 1 (2).

[0069] (3) Graft polymerization to prepare HPMSs / MNPs@PILs dual-site tandem catalyst is the same as step (3) in Example 1.

[0070] The prepared dual-active-site integrated catalyst was used as a catalyst in the tandem reaction of olefin epoxidation and CO2 in-situ cycloaddition, as in Example 1.

[0071] The catalyst yield was 90% as measured by gas chromatography at 90℃ and 1MPa CO2, and remained at 88% after 10 cycles.

[0072] Example 3:

[0073] (1) The preparation of SiO2 hollow porous microspheres with an average particle size range of 300 nm is the same as step (1) in Example 1.

[0074] (2) Preparation of HPMSs / MNPs composite structure by in-situ reduction method

[0075] At room temperature, 1 g of SiO2 hollow porous microspheres obtained in the previous step were added to a mixed solution containing 30 mg of 0.03 wt% chloroauric acid (HAuCl44H2O) solution, 150 g of water, and 0.2 g of polyvinylpyrrolidone (PVP). The mixture was ultrasonically dispersed until homogeneous. Subsequently, 0.01 wt% NaBH4 solution was added dropwise until the solution turned purple. The reaction product was centrifuged and dried to obtain radially porous hollow microspheres loaded with metal nanoparticles.

[0076] (3) Graft polymerization to prepare HPMSs / MNPs@PILs dual-site tandem catalyst is the same as step (3) in Example 1.

[0077] The prepared dual-active-site integrated catalyst was used as a catalyst in the tandem reaction of olefin epoxidation and CO2 in-situ cycloaddition, as in Example 1.

[0078] The catalyst yield was 93% as measured by gas chromatography at 90℃ and 1MPa CO2, and remained at 90% after 10 cycles.

[0079] Example 4:

[0080] (1) The preparation of SiO2 hollow porous microspheres with an average particle size range of 300 nm is the same as step (1) in Example 1.

[0081] (2) The in-situ reduction method was used to prepare the HPMSs / MNPs composite structure, following the same steps as in Example 1 (2).

[0082] (3) Graft polymerization preparation of HPMSs / MNPs@PILs dual-site tandem catalyst and its application

[0083] In a three-necked flask, 0.1 g of hollow SiO2 microspheres loaded with gold nanoparticles, 40 mL of water, 1 g of 1,4-divinylbenzene (DVB), 0.1 g of PVP, 1.5 g of 1-vinyl-3-ethylimidazolium bromide (VEI-Br), and 0.03 g of potassium persulfate were added sequentially. The system was heated to 70 °C under stirring and the reaction was stopped after 10 h. The material was centrifuged and settled, washed alternately with ethanol and water, and dried to obtain the HPMSs / MNPs@PILs dual-site tandem catalyst.

[0084] The prepared dual-active-site integrated catalyst was used as a catalyst in the tandem reaction of olefin epoxidation and CO2 in-situ cycloaddition, as in Example 1.

[0085] The catalyst yield was 91% as measured by gas chromatography at 90℃ and 1MPa CO2, and remained at 88% after 10 cycles.

[0086] Example 5:

[0087] (1) The preparation of SiO2 hollow porous microspheres with an average particle size range of 300 nm is the same as step (1) in Example 1.

[0088] (2) The in-situ reduction method was used to prepare the HPMSs / MNPs composite structure, following the same steps as in Example 1 (2).

[0089] (3) Graft polymerization to prepare HPMSs / MNPs@PILs dual-site tandem catalyst

[0090] In a three-necked flask, 0.1 g of hollow SiO2 microspheres loaded with gold nanoparticles, 40 mL of water, 1 g of 1,4-divinylbenzene (DVB), 0.1 g of PVP, 1 g of 1-vinyl-3-ethylimidazolium bromide (VEI-Br), and 0.04 g of potassium persulfate were added sequentially. The system was heated to 70 °C under stirring and the reaction was stopped after 10 h. The material was centrifuged and settled, washed alternately with ethanol and water, and dried to obtain the HPMSs / MNPs@PILs dual-site tandem catalyst.

[0091] The prepared dual-active-site integrated catalyst was used as a catalyst in the tandem reaction of olefin epoxidation and CO2 in-situ cycloaddition, as in Example 1.

[0092] The catalyst yield was 90% as measured by gas chromatography at 90℃ and 1MPa CO2, and remained at 88% after 10 cycles.

[0093] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing a dual-active-site integrated catalyst, characterized in that, The method includes the following steps: 1) Preparation of SiO2 hollow porous microspheres with an average particle size range of 50–500 nm Isopropanol, hexadecyltrimethylammonium bromide (CTAB), and water were added to a reactor and sonicated until homogeneous. The system was heated to 70–90 °C under stirring, and vinyltrimethoxysilane (VTMS) was added. The mixture was stirred for 20–40 min, followed by the sequential addition of ammonia, tetraethyl orthosilicate (TEOS), and cyclohexane. The reaction was carried out under stirring for 10–15 h, and then the reaction was stopped. The material was centrifuged to settle, washed, and dried to obtain SiO2 hollow porous microspheres (HPMSs). The volume ratio of water:isopropanol:VTMS:ammonia:TEOS:cyclohexane is 130:10-50:0.5-5:1-10:1-5:10-25. Add 0.5–1.0 g of CTAB to every 130 mL of water; 2) Preparation of HPMSs / MNPs composite structure by in-situ reduction method The SiO2 hollow porous microspheres obtained in the previous step were dispersed in water at room temperature and added to a mixed solution containing chloroauric acid (HAuCl4·4H2O), H2O and polyvinylpyrrolidone (PVP). The mixture was ultrasonically dispersed, and then NaBH4 solution was added dropwise until the solution turned purple. The reaction product was centrifuged and dried to finally obtain radially porous hollow microspheres loaded with metal nanoparticles. The mass ratio of HAuCl4·4H2O solution:H2O:PVP = 0.01~0.03:100~200:0.2; each 1g of SiO2 hollow porous microspheres is dispersed in 100~200mL of water; The concentration of the HAuCl4·4H2O solution is 0.01–0.1 wt%. The concentration of the NaBH4 solution was 0.001–0.02 wt%. 3) Graft polymerization to prepare HPMSs / MNPs@PILs dual-site tandem catalyst Hollow SiO2 microspheres obtained in the previous step, water, 1,4-divinylbenzene (DVB), PVP, 1-vinyl-3-ethylimidazolium bromide (VEI-Br), and potassium persulfate (KPS) were added sequentially to the reactor. The system was heated to 60-80°C under stirring and the reaction was stopped after 10-12 h. The material was centrifuged and settled, washed alternately with ethanol and water, and dried to obtain HPMSs / MNPs@PILs dual-site tandem catalyst. The mass ratio is: hollow SiO2 microspheres: DVB: PVP: VEI-Br: KPS = 10~20: 100~150: 10: 100~150: 1~5.

2. The preparation method of the dual-active-site integrated catalyst as described in claim 1, characterized in that, In step 1), the concentration of ammonia water is 25-30 wt%; the stirring speed is 100-200 rpm; and the centrifugation speed is 500-2000 rpm.

3. The preparation method of the dual-active-site integrated catalyst as described in claim 1, characterized in that, In step 2), the concentration of the HAuCl4·4H2O solution is 0.01–0.1 wt%.

4. The preparation method of the dual-active-site integrated catalyst as described in claim 1, characterized in that, In step 3), 0.05–0.1 g of potassium persulfate is dissolved in every 100 mL of water.

5. The application of the dual-active-site integrated catalyst prepared by the method described in claim 1, characterized in that, It is used as a catalyst in a series of reactions involving olefin epoxidation and in-situ CO2 cycloaddition.

6. The application as described in claim 5, characterized in that, Specifically, the steps include the following: The prepared dual-active-site integrated catalyst, reaction substrate, tert-butyl hydroperoxide (TBHP) and N,N-dimethylformamide (DMF) were added to a high-pressure reactor and mixed. After sealing, CO2 was introduced into the reactor and pressurized. The mixture was stirred at 80-100°C for 10-20 h to obtain the product styrene cyclic carbonate. The reaction substrates are styrene, p-methylstyrene, divinylbenzene, or m-methylstyrene; Each 2 mL of DMF contains 50–100 mg of a dual-active-site integrated catalyst, 1–3 mmol of styrene, and 1–10 mmol of TBHP; the CO2 pressure is 0.8–1.5 MPa.

Images